An injector located in an opening in a cylinder head is usually provided in a fuel injection system. The injector serves to inject fuel into a combustion chamber located in the cylinder head. The injector has a valve stem and it should be possible to adjust the rounded projection of said valve stem very precisely in the combustion chamber. An upper section of the injector abuts the valve stem and has a larger cross-section than the valve stem. The upper section of the injector and of the valve stem form a step, which rests on a continuous contact surface of the cylinder head located in the opening. A sealing element is placed between the injector and the cylinder head to seal the combustion chamber off from its surroundings. Generally the sealing element is configured in the form of a perforated disk with a rectangular cross-section perpendicular to the plane of the disk and it is positioned on the contact surface of the cylinder head. As the injector is being fixed in the cylinder head, the sealing element is pressed against the injector and against the cylinder head in such a way that substances in the combustion chamber cannot escape.
The injector must be pressed so firmly against the cylinder head that the sealing element is subject to plastic deformation, to accommodate any irregularities in the cylinder head and the injector. In the case of a sealing element in the form of a disk, the fixing force required to fix the injector in the cylinder head is so large that even the injector could be deformed.